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This work advances the systematic study of the mechanism by which a circular wettability dividing line (WDL) constrains the three-phase contact line of a growing bubble on a surface. This provides critical insights for improving the stability of air layers on superhydrophobic surfaces by discretization, which is essential for improving the application of superhydrophobic surfaces in drag reduction. The effects of two constraint parameters—the radius of the WDL and the size of the surface microstructures—on the growth and detachment behavior of bubbles in a von Kármán swirling flow were experimentally analyzed. The results show that as the WDL radius is increased from 2 to 8 mm, the additional constraint force it generates is weakened, leading to increases in the coefficient of variation of the bubble detachment volume, tilt angle, and asymmetry ratio, and a decrease in its maximum contact width. As the microstructure period is increased from 50 to 100 μm, the number of pinning points provided by the WDL for the three-phase contact line decreases, weakening the constraint force. Consequently, the coefficient of variation of the bubble detachment volume and the asymmetry ratio increase, while the tilt angle and maximum contact width decrease. Finally, as both the radius of the WDL and the size of the microstructures increase, the inertial force grows more rapidly than the buoyancy force at the moment of bubble detachment, resulting in a higher ratio of horizontal to vertical bubble displacement. [ABSTRACT FROM AUTHOR]

Constructing new two-dimensional (2D) van der Waals (vdW) heterostructures has been widely employed as a convenient and effective strategy for tuning the optoelectronic properties, which is of great significance for applications in integrated nano-optoelectronic devices. In this work, we design a GeS/GeSe vdW heterostructure and systematically investigate its electronic and optical properties by using first-principles calculations. Our results indicate that the pristine GeS/GeSe heterostructure possesses an indirect band gap (∼0.98 eV) and exhibits an intrinsically type-I band alignment. Furthermore, the optoelectronic properties of the GeS/GeSe heterostructure can be effectively modulated by applying in-plane strain. Specifically, an indirect to direct band gap transition and a type-I to type-II band alignment transition can be synchronously realized, when the tensile strain along zigzag direction reaches 2%. Furthermore, the calculated dielectric function also reveals an obvious strain effect on the optical properties of the GeS/GeSe heterostructure. The light absorption coefficient of the GeS/GeSe heterostructure along the zigzag direction can reach to 106 cm−1 level, as the compressive in-plane strain reaches −5%. These findings are expected to play a guidance role in the future design of the optoelectronic devices based on 2D anisotropic heterostructures. [ABSTRACT FROM AUTHOR]

Water droplets of varying volumes exhibit distinct behaviors at the tip of a needle under the influence of gravitational force: larger droplets fall from the needle tip, while smaller droplets adhere to the needle tip. By integrating a superhydrophobic hole, which allows the needle to pass through but hinders droplets' passage, a method to allow smaller droplets to fall from the needle was evaluated. The interaction between water droplets and a superhydrophobic hole was studied experimentally, and two phenomena were observed: either the droplet detached from the needle tip or the needle pulled it through the superhydrophobic hole. A critical detachment volume V cri d 0 , D , dependent on the needle diameter d 0 and the superhydrophobic hole diameter D , determines droplet behavior. When the volume of the droplet V droplet > V cri d 0 , D , the droplet detaches from the needle tip. When the V droplet < V cri d 0 , D , the droplet penetrates through the superhydrophobic hole. The results show that the critical detachment volume V cri d 0 , D increases with an increase in d 0 for a given superhydrophobic hole and with an increase in D for a given needle. To enable a 0.25 μl droplet to fall from a 32G needle, a superhydrophobic hole of 0.48 mm diameter was employed. Furthermore, a mechanical model based on force equilibrium was developed to describe the interaction between water droplets and a superhydrophobic hole. [ABSTRACT FROM AUTHOR]